>> Since this request needs to only go to the UA C, we can use its >> Contact address. >> >> This assumes that the Contact is routable from A, but RFC 3261 >> requires that, and if C implements GRUU support, it's likely to be >> true.
As Dale said, it assumes that the Contact is routable from A. If it isn't, then obviously you have to use the address-of record in the To header sent in B's INVITE to C. For example, consider a domain whatever.com where B and C are [EMAIL PROTECTED] and [EMAIL PROTECTED] respectively and B and C have private IP addresses. If a proxy is responsible for the domain whatever.com and if A is from outside that domain, then using the To header is the only way. This way, when A gets the Refer-To [EMAIL PROTECTED], it would just send its subsequent INVITE to the proxy resposible for whatever.com which will then forward it to C. Furthermore, I would've thought that using the addr-of record is always the safer option as it would always get resolved and forwarded to the right place eventually. Is this not true? Regards, Attila >> -----Original Message----- >> From: [EMAIL PROTECTED] >> [mailto:[EMAIL PROTECTED] Behalf Of >> [EMAIL PROTECTED] >> Sent: 19 September 2006 21:43 >> To: [email protected] >> Subject: Re: [Sip-implementors] What URI/URL to use in >> Refer-to header >> >> >> From: "Urquhart, Gord" <[EMAIL PROTECTED]> >> >> Specifically I'm thinking of a case of call transfer, >> where A calls B, >> B calls C and then transfers A to C. >> >> When B sends the REFER request to A, what should the >> URI/URL in the >> Refer-to header contain? >> >> - the URI/URL from the Contact header contained >> in the 200 OK >> returned from C to B in response to B's INVITE >> OR >> - the URI/URL from the To header of the INVITE >> B sent to C. >> OR .... >> >> First, the contents of the Refer-To header is what B wants A >> to put in >> the request-URI of the INVITE that A will send to C. The skeleton of >> the INVITE is: >> >> INVITE C SIP/2.0 >> Replaces: xxx;to-tag=xxx;from-tag=xxx >> Require: replaces >> >> so the URI to be put in the Refer-To header is >> >> C?Replaces=xxx;to-tag=xxx;from-tag=xxx&Require=replaces >> >> Where the xxx's are the dialog identifiers of the dialog >> between A and >> B. >> >> Now what to use for C? >> >> Since this request needs to only go to the UA C, we can use its >> Contact address. >> >> This assumes that the Contact is routable from A, but RFC 3261 >> requires that, and if C implements GRUU support, it's likely to be >> true. >> >> Dale >> _______________________________________________ >> Sip-implementors mailing list >> [email protected] >> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors >> _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
